need help with OBD1

I have a 1992 chevy 1500 pickup. The symptoms are that it seems to go
in and out of "safe mode" or "limp home mode" at
irregular intervals. The truck runs fine but very suddenly will act
like its not getting enough fire to the plugs and an odor of running
veyr rich with a loss of power. It run run like this for several
miles and then suddenly begin running correctly again.

It will do this off and on untill it gradually gets to the point where
it stays in "limp home" type mode.

The cat has been replaced, the coil has been replaced and the wires
with no effect. A buddy says that also when in this "mode"
it appears that half the throttle body is not getting fuel to it????

We replaced the OBD1 computer and the truck ran fine for over 1500
miles and then started acting as before. Replaced that OBD1 computer
with another one and it again ran fine for 400 miles and now is
intermitely acting up again as before.

Any thoughts would be appreciated.

On Tue, 26 Apr 2011 23:46:56 -0500, contender wrote:

> I have a 1992 chevy 1500 pickup. The symptoms are that it seems to go in
> and out of "safe mode" or "limp home mode" at irregular intervals. The
> truck runs fine but very suddenly will act like its not getting enough
> fire to the plugs and an odor of running veyr rich with a loss of power.
> It run run like this for several miles and then suddenly begin running
> correctly again.
>
> It will do this off and on untill it gradually gets to the point where it
> stays in "limp home" type mode.
>
> The cat has been replaced, the coil has been replaced and the wires with
> no effect. A buddy says that also when in this "mode" it appears that half
> the throttle body is not getting fuel to it????
>
> We replaced the OBD1 computer and the truck ran fine for over 1500 miles
> and then started acting as before. Replaced that OBD1 computer with
> another one and it again ran fine for 400 miles and now is intermitely
> acting up again as before.
>
> Any thoughts would be appreciated.


Kinda sounds like something is fu@king with your ECM.

I'd start by looking for a bad ground and then an over-voltage situation.

If you have one left over, open it up and see if something's fried...

contender > wrote:
>I have a 1992 chevy 1500 pickup. The symptoms are that it seems to go
>in and out of "safe mode" or "limp home mode" at
>irregular intervals. The truck runs fine but very suddenly will act
>like its not getting enough fire to the plugs and an odor of running
>veyr rich with a loss of power. It run run like this for several
>miles and then suddenly begin running correctly again.
>
>It will do this off and on untill it gradually gets to the point where
>it stays in "limp home" type mode.
>
>The cat has been replaced, the coil has been replaced and the wires
>with no effect. A buddy says that also when in this "mode"
>it appears that half the throttle body is not getting fuel to it????

Plugs look like they are in good shape? Fuel pressure is good?

Checked all the wiring including the wiring to the O2 sensor? If the O2
sensor drops out, the computer will go into limp home mode. Clean the
connectors, pump a little dielectric grease in there. Do the same for
the engine sensors.

>We replaced the OBD1 computer and the truck ran fine for over 1500
>miles and then started acting as before. Replaced that OBD1 computer
>with another one and it again ran fine for 400 miles and now is
>intermitely acting up again as before.

That sure sounds like the problem isn't the computer, but it might be
the connector going into the computer which you reseated when you replaced
the computer.

>Any thoughts would be appreciated.

Does the computer log any error codes? You really need to be looking at
the codes. 33, 34, 13 maybe?
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."

On 27 Apr 2011 10:15:39 -0400, (Scott Dorsey) wrote:


>That sure sounds like the problem isn't the computer, but it might be
>the connector going into the computer which you reseated when you replaced
>the computer.

He can just remove and reinstall the new computer. If it's fine again
for several hundred miles, then it's probably a loose fitting terminal
in one of the connectors at the ECM.

On Apr 26, 9:46*pm,
(contender) wrote:
> I have a 1992 chevy 1500 pickup. The symptoms are that it seems to go
> in and out of "safe mode" or "limp home mode" at


In order to help we need to know what codes the ecm has stored... (I
am guessing a 43)
You can pull codes with a paper clip, directions are all over google.
HTH and let us know,
Ben

"contender" > wrote in
message ...
>I have a 1992 chevy 1500 pickup. The symptoms are that it seems to go
> in and out of "safe mode" or "limp home mode" at
> irregular intervals. The truck runs fine but very suddenly will act
> like its not getting enough fire to the plugs and an odor of running
> veyr rich with a loss of power. It run run like this for several
> miles and then suddenly begin running correctly again.
>
> It will do this off and on untill it gradually gets to the point
> where
> it stays in "limp home" type mode.
>
> The cat has been replaced, the coil has been replaced and the wires
> with no effect. A buddy says that also when in this "mode"
> it appears that half the throttle body is not getting fuel to it????
>
> We replaced the OBD1 computer and the truck ran fine for over 1500
> miles and then started acting as before. Replaced that OBD1 computer
> with another one and it again ran fine for 400 miles and now is
> intermitely acting up again as before.
>
> Any thoughts would be appreciated.
>

Try removing power to the computer for 10 minutes, then reconnect
(disconnect a battery cable).

See if it then acts like you replaced the computer with a new one.

These computers will store information over time. And for the computer
to set certain codes, it may take several start-up's before enough
data is gathered for the computer to determine something is wrong,
then set a code.

Removing power to the computer causes it to lose its memory, then it
needs to start from scratch gathering data again. And replacing the
computer would do the same thing.

With that said, when the problem occurs, read the computer codes.
Complete troubleshooting information for this is in a factory service
manual set of books for your specific vehicle. (4 books to set.) Order
from your dealer or helminc.com

Also you can get a free diagnostic program for your computer here...
http://winaldl.joby.se

Here is information about the ALDL diagnostic connector...
http://www.aldlcable.com

ALDL codes example...
http://www.gnttype.org/maint/malf.html

FYI - Here is an example of what you need to do for an OBD II computer
to get it to run all the "self tests"....
http://www.obdii.com/drivecycleford.html

Bill Vanek > wrote:
>On 27 Apr 2011 10:15:39 -0400, (Scott Dorsey) wrote:
>
>
>>That sure sounds like the problem isn't the computer, but it might be
>>the connector going into the computer which you reseated when you replaced
>>the computer.
>
>He can just remove and reinstall the new computer. If it's fine again
>for several hundred miles, then it's probably a loose fitting terminal
>in one of the connectors at the ECM.

Yes, precisely!
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

> > On Tue, 26 Apr 2011 23:46:56 -0500, contender wrote:
> >
> > I have a 1992 chevy 1500 pickup. The symptoms are that it seems
to go in
> > and out of "safe mode" or "limp home mode" at
irregular intervals. The
> > truck runs fine but very suddenly will act like its not getting
enough
> > fire to the plugs and an odor of running veyr rich with a loss of
power.
> > It run run like this for several miles and then suddenly begin
running
> > correctly again.
> >
> > It will do this off and on untill it gradually gets to the point
where it
> > stays in "limp home" type mode.
> >
> > The cat has been replaced, the coil has been replaced and the
wires with
> > no effect. A buddy says that also when in this "mode"
it appears that half
> > the throttle body is not getting fuel to it????
> >
> > We replaced the OBD1 computer and the truck ran fine for over
1500 miles
> > and then started acting as before. Replaced that OBD1 computer
with
> > another one and it again ran fine for 400 miles and now is
intermitely
> > acting up again as before.
> >
> > Any thoughts would be appreciated.
> >
> Hachiroku $B%O%A%m%/(B wrote:
>
>
>
> Kinda sounds like something is fu@king with your ECM.
>
> I'd start by looking for a bad ground and then an over-voltage
situation.
>
> If you have one left over, open it up and see if something's
fried...

we had the orginal obd1 and part of the inside did appear to be fried
as in it got too hot. We do not have the replacements as they were
returned under warranty.

just orginally thought it was old age/wore out. what causes an obd1 to
"fry"? I thought there were fuses to protect it from such.

The unusual thing is the OBD1's as in the orginial and the
replacements are not showing any codes on a friends reader which can
read obd1 systems.

On Thu, 28 Apr 2011 18:46:22 -0500, contender wrote:

>
> > > On Tue, 26 Apr 2011 23:46:56 -0500, contender wrote:
> > >
> > > I have a 1992 chevy 1500 pickup. The symptoms are that it seems
> to go in
> > > and out of "safe mode" or "limp home mode" at
> irregular intervals. The
> > > truck runs fine but very suddenly will act like its not getting
> enough
> > > fire to the plugs and an odor of running veyr rich with a loss of
> power.
> > > It run run like this for several miles and then suddenly begin
> running
> > > correctly again.
> > >
> > > It will do this off and on untill it gradually gets to the point
> where it
> > > stays in "limp home" type mode.
> > >
> > > The cat has been replaced, the coil has been replaced and the
> wires with
> > > no effect. A buddy says that also when in this "mode"
> it appears that half
> > > the throttle body is not getting fuel to it????
> > >
> > > We replaced the OBD1 computer and the truck ran fine for over
> 1500 miles
> > > and then started acting as before. Replaced that OBD1 computer
> with
> > > another one and it again ran fine for 400 miles and now is
> intermitely
> > > acting up again as before.
> > >
> > > Any thoughts would be appreciated.
> > >
> > Hachiroku $B%O%A%m%/(B wrote:
> >
> >
> >
> > Kinda sounds like something is fu@king with your ECM.
> >
> > I'd start by looking for a bad ground and then an over-voltage
> situation.
> >
> > If you have one left over, open it up and see if something's
> fried...
>
> we had the orginal obd1 and part of the inside did appear to be fried as
> in it got too hot. We do not have the replacements as they were returned
> under warranty.
>
> just orginally thought it was old age/wore out. what causes an obd1 to
> "fry"? I thought there were fuses to protect it from such.
>
> The unusual thing is the OBD1's as in the orginial and the replacements
> are not showing any codes on a friends reader which can read obd1 systems.


Yes, there are fuses, but we're talking electronics here. It always tries
to seek out a ground, and if the usual path to ground is kaput it will try
to find another way. Example: I had an 80 Corolla I bought brand new. In
1982 (and ~75,000 miles) I stopped to get a cuppa before my 60 mile trip
to work, and it was misting so I had the wipers on delay (delay! A Toyota
with delay!!! (it was a big thing then...))

I puled up nose-in to the GREAT BIG CEMENT WALL, turned the ignition off,
set the parking brake like I always do, took my foot off the clutch...and
the car lurched forward!

Now, i had to get up pretty early to get to work on time, and thought,
"DUMBASS! SHUT THE CAR OFF FIRST!!!!" only to look down and see the keys
dangling from my hand. Then I noticed the charge light and Check Engine
light were on, and the volt meter was measuring about 6 volts! I turned
the ignition on, without starting, and turned it off. Lights and meter
went otu, up to 12 V and back to on and 6V...

Then I shut off the wipers...everything went off...

When I got to work, I called the local Toy Store, and a tech told me one
of the g__ks in the factory overtightened the fuse box ground. I replaced
it with a screw and a washer, and no problems.

So, what happened when the car lurched forward ws, the WHOLE ignition
system was groundng through the windshield wipers!!!

No blown fuses, no other damage. That's why loose or non-conducting
grounds are such a BITCH to troubleshoot! It will find another path to
ground, through whatever it can.

So, I would be looking at the grounds in that area of the vehicle; get a
wiring diagram and trace out the grounds for the ECU. I think that's your
problem.

Good luck!


Er, BTW, it could be a ground to another system on the vehicle. I really
HATE automotive electrical systems...and check out the harness for worn
insulation, too...